The good level of reliability for NGRT indicates that the questions are testing the same construct, namely reading. The types of questions used in NGRT are used in other tests of reading.
Information on Teacher Assessment (TA) levels in Reading for England was collected when the Equating study was conducted in 2012; the correlation between TA levels and the reading ability score was 0.81.
Results were collected from 7,275 Year 6 students who took NGRT and the Key Stage 2 SATS in England in 2016/17. The correlation between NGRT SAS scores and the KS2 Scaled scores in Reading was 0.75 and for the Grammar, Punctuation and Spelling it was 0.72.